Efforts to clean the waterway have led to reduced heavy metal pollution since the late 1990s, Ribeiro said.
20世纪90年代末以来，人们一直努力清理水道，重金属污染已经大大减少，里贝罗说。
This paper analyzes main pollution resources in the heavy oil FCC unit, and introduces some main clean production measures and their results. Then, it offers the improvements.
分析了重油催化裂化装置的主要环境污染源，介绍装置采取的主要清洁生产措施及取得的效果，提出了改进方向。
Having suffered such heavy pollution already, it may now be too late to clean up the river.
这条河流已经遭受很重的污染，现在要清理为时太晚。
Having suffered such heavy pollution already, it may now be too late to clean up the river.
河流已经遭受如此严重的污染，现在要想清理也许太晚了。
Heavy rains will weaken pollution of the water as the lake has no clean water resource. After cut off the sewage of the lake, water quality of the lake was improved.
污染源对湖水水质有重要的影响，在切断了外源污染后，水质有所改善，但水体污染依然严重。
Heavy rains will weaken pollution of the water as the lake has no clean water resource. After cut off the sewage of the lake, water quality of the lake was improved.
污染源对湖水水质有重要的影响，在切断了外源污染后，水质有所改善，但水体污染依然严重。
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